1. Field of the Invention
The present invention relates to a semiconductor device having a semiconductor chip and a wiring member to be electrically connected to the semiconductor chip and a method of manufacturing the semiconductor device.
2. Description of the Related Art
In a semiconductor device, a semiconductor chip and a lead frame incorporating it, are electrically connected by a bonding wire. In a wire bonding step, a ball is formed on the tip of a boning wire, the ball is fixed to the pad on a semiconductor chip. Next, the bonding wire is extended onto the lead frame and connected a lead frame. Thereafter, the bonding wire is cut.
Such a wire bonding technique is disclosed in e.g. JP-A55-118643. The technique disclosed therein relates to awire bonding technique of bonding an Au wire to an Al face. As disclosed in this reference, when the Au wire is fixed to the Al face, intermetallic compound will be generated at the interface therebetween and the boundary is made fragile so that the bonding strength becomes insufficient. In order to overcome such an inconvenience, the invention disclosed in the reference has been accomplished.
However, as the case may be, the semiconductor device manufactured by the above technique cannot also provide sufficient bonding strength under its utilizing environment.
For example, the strength of wire bonding may be reduced according to the chemical state of the surface of the pad of a semiconductor chip, terminal of a package and lead frame. In such a case, the bonding wire is broken when a smaller strength than the strength of a wire strand itself is applied. The inventors of the invention have found that where the wire bonding strength was reduced, the sectional area of the neck portion (just near a ball portion formed at the top end) of the bonding wire had been reduced. If expansion and shrinkage of mold resin of a resin-sealed semiconductor chip, which is thus wire-bonded in such a condition, great strength is applied to a bonding wire of the semiconductor chip. Therefore, the semiconductor device is falied at the portion having a smaller area of the bonding wire.
An object of the invention is to provide a semiconductor device which can prevent reduction in the tension leading to breakage of a bonding wire and a method for manufacturing such a semiconductor device.
A semiconductor device according to the invention includes a lower conductive member, an upper conductive member and a conductive wire. The lower conductive member is formed on a wiring member to be electrically connected to the semiconductor chip. The one end of the conductive wire is electrically connected to a semiconductor chip. The other end of the conductive wire is sandwiched between the lower conductive member and the upper conductive member located thereon and is electrically connected to the wiring member. Thus, the semiconductor chip is electrically connected to the wiring member through the conductive wire.
The connecting portion of the conductive wire to be connected to the wiring member is sandwiched between the lower and upper conductive members so that the neck portion of the conductive wire can be protected from above by the upper conductive member. Therefore, such a structure having both lower and upper conductive members has an increased bonding area of the conductive wire between both conductive members as compared with the structure provided with only the lower conductive member and hence provides an increased bonding strength. Further, the lower conductive member is formed on the lower side of the conductive wire. Therefore, in bonding, the lower conductive member is deformed so that deformation of the conductive wire itself is suppressed and reduction in the sectional area of the neck portion of the conductive wire is also suppressed.
A semiconductor device according to the invention includes a lower conductive member, a second connecting member and a conductive wire. The lower conductive member is formed on a wiring member to be electrically connected to a semiconductor chip. The second connecting member having an upper conductive member formed on said lower conductive member and a connecting portion connected to said wiring member at a different position from said lower conductive member. The one end of the conductive wire is electrically connected so said semiconductor chip. The other end of the conductive wire is sandwiched between said lower and upper conductive members and electrically connected to said lower conductive member.
The neck portion is protected by the upper conductive member. In addition, the lower conductive member to which the other end of the conductive wire is bonded is bonded to the wiring member. The other end of the conductive wire is also bonded to the upper conductive member of the second connecting member. The second connecting member is bonded to the wiring member at a different position from the lower conductive member. Further, since the conductive wire is connected to the wiring member at plural connecting positions, the tension applied to the conductive wire is dispersed at the plural connecting positions. Therefore, since the tension applied to each of the plural connecting positions is reduced on average, even if there is a distribution of the bonding strength, the margin for the limit of the strength leading to flaking of the bonding can be assured.
The semiconductor device according to the invention includes a first connecting member, a second connecting member and a conductive wire. The first connecting member has a lower conductive member formed on a wiring member to be electrically connected to a semiconductor chip and a connecting portion connected to the wiring member at a different position from said lower conductive member. The second connecting member has an upper conductive member formed on said lower conductive member and a connecting portion connected to said wiring member at a different position from said lower conductive member. The one end of the conductive wire is electrically connected to said semiconductor chip. The other end thereof is sandwiched between said lower and upper conductive member and electrically connected to said lower conductive member.
The neck portion is protected by the upper conductive member. In addition, the other end of the conductive wire is bonded to the wiring member through the lower conductive member and also bonded to the upper conductive member of the second connecting member. The first and the second connecting member are bonded to the wiring member at different positions from the lower conductive member, respectively. Therefore, the conductive wire is connected to the wiring member through the lower conductive member and the first and the second connecting member. Thus, the bonding area between the conductive wire and the wiring member is increased so that bonding strength therebetween is increased. Further, since the conductive wire is connected to the wiring member at plural connecting positions, the tension applied to the conductive wire is dispersed at the plural connecting positions. Therefore, since the tension applied to each of the plural connecting positions is reduced on average, even if there is a distribution of the bonding strength, the margin for the limit of the strength leading to flaking of the bonding can be assured.
Preferably, the lower and the upper conductive member and the conductive wire are made of the same material. Because of a metallographic nature, the bonding strength will be made greater between the same kinds of metal than between the different kinds of metal. A wavelength of the light, which the light emitting element and the light receiving element has sensivity, is permeable to the mold resin.
The semiconductor device according to the invention preferably includes mold resin for sealing the semiconductor chip and wiring member. The semiconductor chip can include at least one of a light emitting element and a light receiving element. The light relative to the light emitting element and light receiving element is preferably permeable to the mold resin.
Where the semiconductor device is sealed by mold resin, its strength for the stress applied when the mold resin is expanded or shrunken can be increased. Particularly, such a semiconductor device is suitable when it is molded by transparent resin because the transparent resin and the wiring member such as a lead frame have different thermal expansion coefficients.
The present invention relates to a method of manufacturing a semiconductor device in which a semiconductor chip and a wiring member are electrically connected to each other. Therefore, the invention comprising the steps of (1) a first step of forming a lower conductive member on said wiring member; (2)a second step of connecting the one end of a conductive wire to said semiconductor chip; (3) a third step of connecting said conductive wire to said lower conductive member; and (4) a fourth step of forming an upper conductive member on said lower conductive member through said conductive wire.
Since the lower conductive member is provided before the conductive wire is connected to the wiring member, the conductive portion can be provided which can absorb the stress applied in bonding to the portion to which the conductive wire is connected. Therefore, the deformation of the conductive wire can be decreased. Further, since the upper conductive member is provided on the lower conductive member through the conductive wire after the conductive wire has been connected to the lower conductive member, the neck portion of the conductive wire formed when the conductive wire is connected to the lower conductive member can be protected.
The method of manufacturing a semiconductor device according to the invention can further comprise, after said fourth step, (5) the step of fixing a conductive portion extending from said upper conductive member to said wiring member at a different position from said lower conductive member.
The upper conductive member protects the neck portion and is bonded to the conductive wire. Therefore, if the conductive portion extending from the upper conductive member is bonded to the wiring member, the entire bonding strength is increased.
The method of manufacturing a semiconductor device can further comprise, prior to said second step, (6) the step of bonding a conductive portion extending from said lower conductive member to said wiring member at a different position from said lower conductive member.
The lower conductive member is bonded to the conductive wire. Therefore, if the conductive portion extending from the lower conductive member is bonded to the wiring member, the entire bonding strength is increased.
The method of manufacturing a semiconductor device according to the invention can, further comprises (7) a step of preparing the semiconductor chip having one of a light receiving element and a light emitting element and the wiring member prior to said first step; and (8) a step of sealing said wiring member and said semiconductor chip connected to said wiring member through said conductive wire using mold resin.
After the neck portion is protected by the upper conductive member, the wiring member and semiconductor chip are sealed by mold resin. When stress is applied to the conductive wire owing to the expansion and shrinkage of the mold resin for sealing, the breakage of the conductive wire at the neck portion is difficult to occur. The light relative to the light receiving element and the light emitting element is permeable to the mold resin.
In the semiconductor device and the method of manufacturing it according to the invention, the wiring member may be a lead frame on which the semiconductor device is mounted, or another semiconductor chip different from the semiconductor chip. Thus, the present invention can be applied to both cases where the wiring member is the semiconductor chip and lead frame.